The present invention relates to supports for photographic use, a preparation method thereof and photothermographic materials by use thereof.
In the field of graphic arts and medical diagnosis, waste liquor produced in wet-processing of image forming material results in problems and further reduction of processing effluent is strongly desired in terms of environmental protection and space saving. Accordingly, a technique for photothermographic materials is required which enables efficient exposure by means of a laser image setter or a laser imager and formation of black images exhibiting high resolution and clearness. As such a technique is known a thermally developable photothermographic material which comprises on a support an organic silver salt, light sensitive silver halide grains, reducing agent and a binder, as described in U.S. Pat. Nos. 3,152,904 and 3,487,075, and D. Morgan xe2x80x9cDry Silver Photographic Materialxe2x80x9d, Handbook of Imaging Materials, Marcel Dekker, Inc. page 48 (1991). These photographic materials, which are developed at a temperature of 80xc2x0 C. or higher, are called a thermally developable photothermographic material (hereinafter, also simply denoted as a photothermographic material).
Plural color-separation film sheets prepared from photographic material for graphic arts use are used to undergo color printing. Each of such color separation films is printed onto a printing plate and color printing is made by superposition thereof. When plural color separation films are superposed, if the superposition is not entirely identical, a phenomenon such as doubling occurs in printing. Accordingly, in photothermographic materials for use in plate-making, prevention of thermal dimensional change is one of important problems in photothermographic materials for use in plate-making.
Photographic materials for use in printing plate making are often used by taking out a necessary amount from the roll form, in terms of simplicity and space-saving. When using such a roll film, roll set curl produces a problem in operation. Thus, in cases when such roll set curl is marked, there are such problems that the film cannot be straightly cut with an automatic cutter, the thus cut film cannot be finely superposed and close contact with an original at the time of exposure is poor. Specifically, in the case of a thermal developing system, poor contact with a heat-developing roll results in serious troubles such as uneven development.
The present invention was proposed to overcome the foregoing problems. Thus, it is an object of the present invention to provide a photothermographic material for use in printing plate-making, specifically suitable for multiple plate printing, which exhibits superior dimensional stability even when subjected to thermal development at a high temperature and little roll set curl when used in a roll form, and a photographic support used in the photothermographic material, and a polyester film.
The above object of the invention can be accomplished by the following constitution:
1. a polyester film, wherein, when subjected to a tensile viscoelasticity measurement, the polyester film exhibits a minimum value of not more than 0.15 with respect to a tan xcex4 value obtained at a frequency of 0.01 Hz within the temperature range of 100 to 160xc2x0 C., the tan xcex4 value being determined in a tensile viscoelasticity measurement;
2. a photographic support comprising a polyester film as described in 1. above;
3. a photothermographic material comprising a support having thereon an organic silver salt, a silver halide and a reducing agent, wherein the support comprises a polyester film as described in 1. above.